[Radiance-general] mirror material ignoring modifier in virtual source calculations

[Greg Ward]

Hi Rioboo,

Your bat file only creates a single rendering with a single solar position.  In fact, I don't understand the output, which looks much darker than it should be for direct solar illumination.  Are you rendering different solar angles?  Can you do it with a simpler test case, like a single piece of glass with your mirror parallel to a diffuse surface that does not face the sun?  If you ran that at different solar incident angles, the value divided by the cosine of the incident angle (to account for grazing sunlight) should follow the Fresnel approximation you are using.

Cheers,
-Greg

> From: goodriver laurus <rioboo at gmail.com>
> Date: June 13, 2016 11:56:25 AM PDT
> 
> Hi Greg,
> I am sending you a simple test with my results, so you can have a look if you have the time. I have included a small batch file to run the calculation under MS-DOS (I had to change the extension to bat2 in order to avoid the attachment to be blocked).
> In answer to your questions:
> 1- I was testing different sun positions, but the test attached includes only one. This should suffice to try different angles of incidence, since every reflector has a different orientation.
> 2- I am not sure if I understand this point. I do see different values where direct and reflected components converge, is that the question?
> 3- I checked the normals and they point outwards, but I guess that was expected since I can see the reflections and the camera is located outside the buildings.
> I greatly appreciate your help, this issue is really puzzling me.
> Many thanks,
> Rioboo
> 
> Hi Rioboo,
> 
> Your definition looks correct to me.  What different conditions are you using to make this determination?
> 
> 1) Do you change the angle of the sun?  This is the only way to test different angles on the mirror, since the sun is a collimated source of light.
> 
> 2) When you change the solar angle, do you move your point or at least ensure that it remains in the reflected beam?  If it sees sunlight directly as well, you will need to look for variation in the 8-80% that is reflected (depending on angle).
> 
> 3) Are you sure your mirror surface normal faces outwards?  If it faces inwards, like most windows in Radiance, then the mirrored sources will only happen on the interior.
> 
> Cheers,
> -Greg
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